The present invention relates to fasteners for releasably and integrally securing otherwise movable parts, and more particularly to fasteners for fixing moveable components to adjust wheelchairs, carseats and other support devices, especially those designed to accommodate physically challenged individuals.
Wheelchairs, carseats for children, and similar support devices typically include components that are movable relative to one another to adjust arm rests, chair backs and other elements to accommodate persons of different sizes and having different physical needs. Frequently these components have slots or other openings to facilitate their coupling with nut/bolt fastening arrangements in which a threaded shank of the bolt extends through the openings of the components, and the components are contained between the nut and a head of the bolt. To facilitate coupling and release, the bolt can have a carriage feature, i.e. a square shank portion near the head, to counteract the tendency to rotate within the slot and thus facilitate securing the fastener by turning the nut. The carriage feature functions satisfactorily, however, only if the transverse (non-axial) dimension of the square is substantially equal to the width of a slot through which the bolt extends.
These fastening arrangements are prone to other difficulties including the need for tools to tighten the arrangement sufficiently to insure a secure connection, the risk of loosening or unintentional release when the arrangement is subject to vibration, protrusions or sharp edges that present a risk of injury to the individual using the support device and others, and the risk of damage to the components due to over tightening of the fastener.
Moreover, such fasteners preferably should include a means for positively retaining elements of the fastener to prevent unintentional removal and loss of one or more elements, and a means for positively locking the fastener to more securely fix the adjustable components.
A wide variety of fasteners and fastening assemblies are used in adjusting support devices, and more generally in mounting objects and connecting pieces (e.g. of sheet metal) together. For example, U.S. Pat. No. 5,205,692 (Kelbert) discloses a fastener including a bolt with an internally threaded collar that also has external threads to receive a nut and integral washer. A panel can be secured between a head portion of the bolt and the washer. The washer has elastically deformable ribs that press against the panel when the arrangement is tightened to provide a water tight seal.
U.S. Pat. No. 2,802,997 (Bronkhurst) involves a fastening mechanism including an externally threaded rod that fits into an internally threaded block. The rod further has internal threads at one end to receive a screw that provides a stop. At the other end of the rod is a wing nut and a conical washer. A multi-threaded arrangement in which the screw threads at different locations have different pitches, is shown in U.S. Pat. No. 941,031 (McBean). The purpose of the different pitches is to enable locking of the assembly at different axial positions.
In U.S. Pat. No. 2,047,241 (Wittel), a nut member with internal threads is threaded onto a spindle. The nut member has a notch that accommodates a pin fixed to a plate, thus to prevent the nut from rotating when sufficiently close to the plate.
These arrangements, while perhaps suitable for their intended purposes, fail to adequately address the needs noted above in connection with the support devices, whether intended for children or adults.
Therefore, it is an object of the present invention to provide a fastener that is more convenient to use and establishes a more reliable connection of adjustable components, even when the components are subject to vibration.
Another object is to provide a fastening apparatus that provides a secure connection of adjustable components without presenting sharp edges or protrusions.
It is a further object to provide a fastener for securing adjustable components, with fastening elements that can be selectively locked at a variety of positions relative to one another, to accommodate components of different sizes and to selectively allow limited freedom of movement of the elements relative to one another.
Yet another object is to provide a fastener for adjustable components that can be operated by hand to secure and release adjustable components, and alternatively locked to prevent a release of coupled components by hand.